1. Field of the Invention
The present invention relates to a non-destructive testing equipment having a SQUID type magnetic sensor. More specifically, the present invention relates to a new magnetic testing equipment which can continually detect impurities or defects contained in an object to be tested, with high sensitivity.
2. Description of Related Art
Wire-rod materials such as optical fibers, cables and wires, and plate-like metal or ceramics materials which can be used for a body of aircraft or spacecrafts and satellites, have an extremely large length or a large area. On the other hands, extremely small impurities or slight defects included in these materials will results in serious troubles and damages. Therefore, severe quality control has been required for these materials.
In turn, in signal cables composed of signal conductors, insulators and tensile strength members in combination, individual component parts can be tested before the component parts are assembled to a cable. However, there is no method for detecting internal defects or presence of impurities in the cables after the cables have been completed. Therefore, the testing of the completed cables had to rely upon a partially destructive sampling inspection in which one or more cables are sampled from a lot of completed cables, and then, the sampled cables are broken and tested.
Furthermore, wire-like materials and rod-like materials have been continuously produced in an industrial production scale as elongated products, and then, have been used as elongated products. As explained above, if even only a portion of these elongated materials contains a small defect, a total function of these elongated materials is subjected to very serious influence. Accordingly, during a production process, it is desirable to test the whole of the elongated materials. However, there has not yet been a non-destructive testing means that can precisely and efficiently inspect the whole of the elongated materials so as to find out an internal defect during a manufacturing process of the elongated materials.